With the advance of the application software for image drawing, images having a variety of colors and patterns are processed and edited on personal computers (PC) and work stations (WS).
Further, with the advance of the image forming devices using the electrophotography method, the ink jet method, and the like, it has been made possible to print the images created by such application software on paper or the like with high precision.
Conventionally, when a composite image having an overlapping area where parts of different images (figures), characters, and the like are overlapped one over another is to be represented by using application software, an image having a higher priority rank has been preferentially represented on the basis of priority ranks (display order) which are normally established for the images.
On the application software, such a composite image is handled as if, in the overlapping area, both images were given. Conventionally, when an image is to be formed with an image forming device, only the image which priority rank is higher has been formed into an image if it is opaque. On the other hand, if the image having a higher priority rank is transparent, the image processing has been separately applied to the overlapping area so as to form an image in which both the images are blended into one.
This is because, for example, when the image which priority rank is higher is opaque, the image which priority rank is lower will not show up to the surface, thus there is no need for forming the image having a lower priority rank into an image. If the image which priority rank is higher is formed into an image on the image formed from the image having a lower priority rank, the geometry and color of the image with a lower priority rank can have an influence on the image having a higher priority rank.
As an example of such a technology, JP H09-104987 A discloses the technology which, by writing a divided job sequence into a map memory, and developing the pixel information in accordance with the result of the overlapping judgment, efficiently carries out detection of the drawing elements which are overlapped one over another, thus preventing the effect of the parallel processing of drawn images from being cancelled.
In recent years, with the advance of the image processing apparatus, there have arisen various demands for the processing up to the stage of image formation.
For example, in order to introduce the electrophotography type image forming device, which eliminates the need for photochemical process, into the light printing market, an electrophotography type image forming device which can provide a still higher quality of image has been required.
In some applications of the electrophotography, there arises a case in which images are formed having a different attribute, such as an embossed image, which has an attribute of height in addition to that of planarity using only color toners, such as embossed printing with which an embossed image is formed by using foaming toners in addition to the conventional color toners.
With these technologies, how the image formation is carried out in the area where the toners are overlaid one over another (in the overlapping area where images are overlapped one over another) is an extremely important problem.
With conventional image forming devices, however, an area where images are overlapped one over another, and an area where images are not overlapped have been differently processed for image formation. Thus, such a problem arose that an error is caused between the respective areas, resulting in a gap being produced at the boundary between the images formed. Also, when the image having a higher priority rank is to be overlapped on the image with a lower one so as to generate a delicate expression for the image formed, it was very difficult to cope with the situation.
In addition, in such a case as that when images having different attributes, i.e., a planar image, which is represented on a planar surface only with color toners, and an embossed image, which represents a height by using foaming toners, are to be represented, it is desirable to carry out image formation also for the image with a lower priority rank.
In view of the above problems, the purpose of the present invention is to provide an image forming device which is capable of adequately forming an image for the areas where images are overlapped one over another.